User Guide
3.10. Apply a patch from someone else
Sometimes you need to apply a patch to your private source tree. Maybe because you want to try a
patch from someone on the developer mailing list, or you want to check your own patch before sub-
mitting.
Warning!
If you have problems applying a patch, make sure the line endings (CR/NL) of the
patch and your source files match.
3.10.1. Using patch
Given the file "new.diff" containing a unified diff, the right way to call the patch tool depends on
what the pathnames in "new.diff" look like. If they're relative to the top-level source directory - for
example, if a patch to "prefs.c" just has "prefs.c" as the file name - you'd run it as:
patch -p0 <new.diff
If they're relative to a higher-level directory, you'd replace 0 with the number of higher-level direct-
ories in the path, e.g. if the names are "wireshark.orig/prefs.c" and "wireshark.mine/prefs.c", you'd
run it with:
patch -p1 <new.diff
If they're relative to a subdirectory of the top-level directory, you'd run "patch" in that directory
and run it with "-p0".
If you run it without "-p" at all, the patch tool flattens path names, so that if you have a patch file
with patches to "Makefile.am" and "wiretap/Makefile.am", it'll try to apply the first patch to the top-
level "Makefile.am" and then apply the "wiretap/Makefile.am" patch to the top-level "Makefile.am"
as well.
At which position in the filesystem should the patch tool be called?
If the pathnames are relative to the top-level source directory, or to a directory above that directory,
you'd run it in the top-level source directory.
If they're relative to a subdirectory - for example, if somebody did a patch to "packet-ip.c" and ran
"diff" or "svn diff" in the "epan/dissectors" directory - you'd run it in that subdirectory. It is pre-
ferred that people NOT submit patches like that - especially if they're only patching files that exist
in multiple directories, such as "Makefile.am".
3.10.2. CVS diff (obsolete)
One other thing to note - "cvs diff" produces output that at least some versions of "patch" can't
handle; you'd get something such as
Index: missing/dlnames.c
===================================================================
RCS file: /tcpdump/master/tcpdump/missing/dlnames.c,v
retrieving revision 1.5
diff -c -r1.5 dlnames.c
*** missing/dlnames.c 18 Nov 2003 23:09:43 -0000 1.5
--- missing/dlnames.c 31 Aug 2004 21:45:16 -0000
***************
from "cvs diff -c", and something similar from "cvs diff -u", and "patch", unfortunately, would use
the "diff -c" or "diff -u" line and try to patch "dlnames.c" in the directory you're in, rather than in the
Work with the Wireshark sources
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